The present invention deals with a manipulator with electromagnetic detent for the driving servo-control of hydraulic mechanisms.
Function of electromagnetic detents is locking the driving servo-control in particular positions in order to allow the continuous operation without the operator acting on the manipulator handle or joystick for the whole execution time. Object of the present invention is adding a possible action on pushers next to the one pressed with active coupling, allowing a manipulator rotation that is orthogonal to the one allowing its locking. The introduction of this movement has required an improvement of kinematism efficiency in order to avoid relative movements between plate and coupling device, to remove rubbing phenomena between these two components and reducing the contact wear.
Manipulators are already known that are equipped with electromagnetic detents, such as the one disclosed in U.S. Pat. No. 4,827,982, that provide an electromagnet or a solenoid in a fixed position integral with the driving valve case and a ferromagnetic plate integral with the manipulator lever.
This type of solution does not allow the above-described crossed movement, further pointing out different problems related to the positioning of various kinematism components, especially when this construction system is applied to servo-controls with more that two controlled axes. In fact, while in this latter case the alignment between plate and solenoid is guaranteed by the kinematism structure, in the case with four controlled axes there are two orthogonal rotations usually due to a universal joint or a ball joint.
This implies a possible misalignment of the plate with respect to the solenoid, with coupling accuracy problems.
Also in the arrangement disclosed in U.S. Pat. No. 4,777,981, for every position, an electromagnet or solenoid is provided, that is supported by a plate that can vertically translate in contrast with a spring action. In the electromagnet centre, a tooth is provided that is adapted to be inserted into a notch obtained in a plate hinged to the joystick control rod.
This arrangement ensures the coupling position, but the wear problem has not yet been solved; instead, this latter problem has been made more pronounced due to the rubbing action of the tooth onto the plate.
A manipulator is also known that is described in EP 1047985 with a plate secured to a cam that is able to be actuated by the manipulator control rod, in order to be able to rotate around a shaft whose axis is placed on a plane defined by the servo-control body axis and the axis on which the servo-control signal generator moving member is arranged.
In said manipulator, guiding means are provided that are composed of a curvilinear track that is integral with the servo-control body on which a slider can slide, such slider being integral with the shaft around which the ferromagnetic plate can rotate.
The electromagnet is secured to the servo-control body.
An arrangement is also provided in which the electromagnet is secured to the shaft supported by the cam and the plate is in a fixed position.
This solution allows the simultaneous movement of nearby actuators upon coupling, optimally solving the sliding, and therefore wear, problem between electromagnet and plate, but it transfers said phenomenon between slider and track, in addition to be of a cumbersome and encumbrant construction.